High speed serial printer with plural hammers

ABSTRACT

A high-speed on-the-fly serial printer, wherein a rotating typecarrying member moves along a print line past a plurality of printing positions, wherein a plurality of hammers are mounted to move with said type-carrying member, and wherein said hammers are selectively actuated in accordance with the position of said carriage to drive the type-bearing element of said type-carrying member against a print-receiving motion to effect character printing thereon.

United States Patent [191 Boss! [451 Nov. 20, 1973 HIGH SPEED SERIAL PRINTER WITH PLURAL HAMMERS [75] Inventor:

[73] Assignee: Honeywell Information Systems Italia, Caluso, Italy 22 Filed: Mar. 11,1971

21 App1.No.: 123,277

Oscar Bossi, Milano, Italy [30] Foreign Application Priority Data 3,356,199 12/1967 Robinson 197/53 X 3,371,766 3/1968 Staller 197/53 3,384,216 5/1968 Thayer..... 197/53 X 3,388,782 6/1968 Schwend 197/49 3,542,182 11/1970 Langenberger. 197/18 3,565,230 4/1968 Webberley 197/49 3,589,494 6/1971 Gloess 197/18 Primary Examiner-Edgar S. Burr Attorney-Fred Jacob, Ronald T. Reiling and Lewis P. Elbinger [57] ABSTRACT A high-speed on-the-fly serial printer, wherein a rotating type-carrying member moves along a print line past a plurality of printing positions, wherein a plurality of hammers are mounted to move with said typecarrying member, and wherein said hammers are selectively actuated in accordance with the position of said carriage to drive the type-bearing element of said type-carrying member against a print-receiving motion to effect character printing thereon.

4 Claims, 9 Drawing Figures PAIENIEDRMPO @915 P OI Pm moEm Oscar INVENTOR.

ATTORNEY.

Pmmmm 20 ms 3; 773; 1 s1 PRIOR ART FIG. 2a FIG. 2b

M PRIOR ART M PRIOR ART [PDQ FIG. 3 FIG. 4

Q 55 57 W/ M 7/ Wk/ U H p 55 FIGS "l Oscar 5055/ INVENTOR ATTORNEY.

PMENIEUIIIIIIPO I975 3,773,161

SHEET 3K? 3 SENSOR V COUNTER COMPARISON 69 C CIRCUIT ACTUATING ACTUATING 75 CIRCUIT CIRCUIT 76 Fig.7.

SENSOR COUNTER :q: ACOMPARISON 69 CIRCUIT ;'I

SENSOR V 83 Fli 87 88 /84 AACTUATING ACTUATING 4 89 CIRCUIT CIRCUIT 86 5 A85 II\'\'E.\"I()R OSCAR BOSS! .2 lg'.8. y

ATTORNEYS HIGH SPEED SERIAL PRINTER WITH PLURAL HAMMERS BACKGROUND OF THE INVENTION The present invention relates to serial high-speed impact printers employing the on-the-fly principle of printing and more particularly to such printers which can be defined as front striking printers, i.e., which accomplish printing by means of a printing hammer and a strike resisting platen, or printing bed.

In such printers, a type-carrying member consisting, for example, of a group of flexible reeds arranged radially with characters provided in relief on the extremities of said reeds, is maintained in appropriate motion so that all of the characters of the type-carrying member pass sequentially through a predetermined printing position. The type-carrying member is mounted on a printing carriage on which the printing hammer is mounted, and the entire carriage assemblage moves either by a continuous or a step-by-step motion along the print line. Alternatively, the type-carrying member may consist of a flexible belt which runs along the print line and only the printing hammer is carried by the printing carriage.

For some types of such printers in which the motion of the type-carrying member is correlated with the printing motion, and for other types in which, by electronic means, there is provided the capability of accomplishing corrections in the position of printing by operating with appropriate delays in the moment of printing (as is, for example, described in the US. Pat. application Ser. No. 108,787, filed Jan. 22, 1971 in the names of Castoldi et al., and assigned to the same assignee as the present application), the situation may occur that two characters to be printed in two adjacent printing positions require consecutive operations of the printing hammer in a very short time.

In this case an inconsistency problem arises due to the hammer printing time and the hammer recovery time, which is the time required for the hammer, after having accomplished a printing operation, to return to its original rest position so as to be in condition to correctly perform subsequent printing of a character in response to a new printing command.

This disadvantage has been overcome today in the so-called synchronous printers, i.e., printers in which the printing carriage motion is correlated with the motion of the type-carrying member, by providing a sector, or segment, of the type-carrying member free of characters and of appropriate width, between an initial character and a last character of the character set.

This solution has the disadvantage that a portion of the type-carrying member is unused and, as a consequence, the speed with which the characters of the set pass through the printing position is considerably greater than the speed which would be obtained by using the entire type-carrying member for the same rate of printing. This causes an impression of poor quality, resulting from a smearing of the printing in the direction of the motion of the characters relative to the print-receive member.

Alternatively, to improve the quality of the printing it is necessary to reduce the character speed and, consequently, to reduce the rate of printing, i.e., the machine performance. Accordingly, it is the object of the present invention to provide an improved on-the-fly serial printer.

SUMMARY OF THE INVENTION These disadvantages are eliminated by the printing device of the present invention by providing for, two distinct printing hammers to operate selectively in two distinct phases of motion of the printing carriage and on two distinct sectors of the type-carrying member (fixed in the case of synchronous printers and variable in the case of asynchronous printers), thereby permitting the successive printing of two characters in consecutive printing positions and with a very short interval of time (in the limit a zero interval) from one to the other.

BRIEF DESCRIPTION OF THE DRAWING The invention will be described with reference to the accompany drawing, wherein:

FIG. 1 is a schematic perspective view of a serial printer of the prior art;

FIGS. 2a and 2b show schematically a portion of the character member of the printer of FIG. 1 at two different times;

FIG. 3 illustrates a solution used in the prior art printers for improving their performance;

FIG. 4 illustrates another solution for improving the performance of these prior art printers;

FIG. 5 is an upper view of an arrangement according to present invention for improving the performance of a serial printer;

FIG. 6 is an elevational view of the arrangement of FIG. 5;

FIG. 7 is a block diagram of a preferred controlled circuit for the printing device of the invention; and

FIG. 8 is a block diagram of a controlled circuit for the printing device of the invention, particularly advantageous for use with an asychronous printer.

DESCRIPTION OF THE PREFERRED EMBODIMENT The prior art serial printer of FIG. 1 is of the synchronous type. Such printer consists of a frame 1 in which is disposed a printing carriage 2 slidably mounted on rotatable prismatic guides 3 and 4. Printing carriage 2 supports a printing hammer 5 actuated by an electromagnet 6 and a character, or type-carrying member 7 consisting of a plurality of radial reeds, or blades, 8. Characters are provided in relief, each on the extremity of a reed 8.

Character member 7 is mainted in rotation through a conical gear couple 9 and the prismatic guide 4 by a motor 10. A code or timing disc 11 is keyed to the shaft of motor 10. Disc 11 cooperates with sensors 12 and 13 (optical, magnetic, and the like), which supply suitable pulses for character timing and recognition.

Due to the rotation of type-carrying member 7, the different characters thereon pass sequentially between printing hammer 5 on one side thereof and inking ribbon l4, print-receiving medium and platen on the other side thereof. Upon enerization of electromagnet 6 at a predetermined time determined by the timing devices, the desired character is imprinted on the printreceive medium.

Motor 10 also drives in rotation, in addition to typecarrying member 7, the threaded shaft 18, through a gear couple 17. The thread of shaft 18 has a pitch equal to the distance between two adjacent printing positions. A tooth I9, fastened to printing carriage 2, normally engages threaded shaft 18 whereby due to the rotation of shaft 18 itself, the printing carriage moves along the print line.

The tooth ratios of gear couple 9 and gear couple 17 are such that for each revolution of character member 7 printing carriage 2 moves a pitch, or the distance between adjacent printing positions.

A rotating electromagnet 20 responds to a carriage return command to rotate prismatic guide 3 and disengage tooth 19 from the thread of shaft 18, whereupon a spring 21, acting through a cable 22 and return pulley 23 restores carriage 2 to its initial position.

Other devices, not described herein, control inking ribbon 14 to advance and provide for the intermittent movement of the print-receiving medium 15.

For a better understanding of the instant invention, the mechanism of printing on-the-fly will now be described. For this purpose, FIG. 2a represents a portion of the type-carrying member at a particular instant. The rectangles 31, 32, and 33 represent three successive printing positions along the print line. In the instant considered, assumed to be an initial" instant, the axis of rotation of the type-carrying member is aligned midway between printing positions 31 and 32. In this initial instant a radial reed 35, the extremity of which bears the alphabetic character A, is precisely opposite to printing position 32. Thereby, by energizing the printing electromagnet at such instant it is possible to effect the printing of the letter A.

The head of the printing hammer, represented by the dotted rectangle 36, has a width sufficient to act in two printing positions, i.e., positions 31 and 32 of FIG. 2a. The reason for this will be clarified hereinafter.

Assume further that the direction of rotation of the character member, as seen in FIG. 2a, is counterclockwise. Therefore, the succession of characters B, C, I), etc. of the character set will pass sequentially through position 32. Simultaneously, the type-carrying member and the entire printing carriage (including the printing hammer) will move towards the next printing position 33.

When the character reed 37, bearing the alphabetic character Z (the last character of the set), is opposite to printing position 32, the axis of rotation of the character member will be almost midway between printing positions 32 and 33. This instant is represented in FllG. 2b, and in this situation the printing hammer is now opposite to printing positions 32 and 33. Therefore, the printing hammer must have a width sufficient to provide for printing a character during the entire motion of the printing carriage through a printing pitch.

Assume, next, that the character Z is to be printed in printing position 32. This printing will occur with the apparatus disposed as represented in FIG. 2b. If, now, the character to be printed in the next position 33 is the letter A, and such letter were on the immediately following reed 38, printing would not, in general, be possible, because the hammer operation time is usually a few milliseconds whereas the characters pass through a printing position at intervals of some hundredths of milliseconds.

Accordingly, to provide in any instance for the printing of the last character of the set (the letter Z in the instant example) in a printing position and the printing of the first character of the set (the letter A in the instant example) in the immediately following printing position, it is necessary to provide an angular spacing between the first and last characters. This angular spacing must be sufficient to provide an interval between the passage of the two characters 2 and A through the printing position equal to or greater than the operation time (printing and return to rest position) of the printing hammer. This requirement is represented in FIGS. 2a and 2b by the provision of three reeds without characters between reeds 35 and 37. With the operation time of the printing hammer, the peripheral speeds commonly adopted for the type-carrying member, and the angular distance usually occupied by each character, this requirement reduces the performance of the printer by 20 to 40 percent.

Another problem, which is demonstrated by FiGS. 2a and 2b, is the need to suitable space the character reeds, relative to the printing hammer width, in order to avoid double printing and the phenomenon known under the name of interference and described, for example, in US. Pat. application Ser. No. 54,814, filed July 14, 1970, and assigned to the same assignee as the present application. It is known that this problem may be solved by using character reeds having on their reverse sides, in correspondence with the characters to be printed, tapered projections to which the required pressure is applied by the printing hammer, which in turn, has a reduced transverse dimension.

Such solution is represented for example in FIG. 3 and, in the limit, by reducing the transverse dimension of the contact surfaces between hammer and projections to zero, it is possible to reduce the width of the printing hammer to the printing pitch. Thus, in such limit it is possible to arrange the character reeds very close together, i.e., with a spacing not much greater than the printing pitch.

The above-mentioned US. Pat. application Ser. No. 54,814 describes another method of eliminating the disadvantage mentioned above by using two overlapping printing hammers, each hammer cooperating with a sequence of alternate characters on top of the typecarrying member. For this purpose the reverse sides of the character reeds are provided with suitable projections. These projections are disposed alternatively in two rings that all the projections of one ring cooperate with one hammer and all those of the other ring with the other hammer. Such solution is represented schematically in FIG. 4, wherein the character reeds are shown in section to demonstrate the projections in two alternate rings.

FIGS. 5 and 6 represent, on the other hand, a solution according to the instant invention, which provides for eliminating completely the disadvantages mentioned above, including the restraints imposed by the printing hammer recovery time. Briefly, the invention consists of the joint use of two printing hammers, disposed on two different levels and partially overlapping, and cooperating with a tapered projection arranged on the rear of each reed of the type-carrying member. A first printing hammer S1 is hinged on a pivot 52. The printing head of hammer 5 has a width L greater than one-half of a pitch, and preferably very close to said pitch. A second printing hammer S3 is hinged on a pivot 54. The printing head of hammer 53 has a width equal to that of the head of hammer 5H.

jection 55 disposed on the reverse side of each character reed. The height H of such projections (FIG. 6) is such as to permit the cooperation of a projection with either one of the two hammers 51 and 53.

Hammers 51 and 53 are mounted on the printing carriage and are actuated so that each effects the printing of any character included in a respective first and second half of the type-carrying member. The following example will clarify the principle on which the invention is based.

Assume, first, that a reed 56 (FIG. 5) is provided with the alphabetic character A and that reed 56 is in the proper position to effect printing. The printing of the character A may, therefore, be accomplished by hammer 51, but not by hammer 53.

As the following reeds 57, etc. move from right to left to enter the printing position the group of hammers 51 and 53 moves to the right. Therefore, there will be an intermediate character of the assembly which will be in the printing position when the two hammers have so moved with respect to the printing position as to permit printing with either hammer 51 or hammer 53.

For the later characters, the continuing motion of the two hammers toward the right with respect to the predetermined printing position permits printing only with hammer 53. At the conclusion of such motion, hammer 53 will be positioned to provide for printing of the last character of the set, while hammer 51 will be in position to provide for printing the first character of the set in the next-adjacent printing position.

Thus, with this invention, it is no longer necessary to provide an appropriate spacing between the first and last characters of the assembly, whose printing is not accomplished with two distinct hammers.

With the arrangement of the invention and the use of the two hammers a dual benefit is realized. On the one hand, it is possible to solve the problem created by the operation time of the printing hammer, and on the other hand, the cross-sectional dimension of the printing hammer may be reduced, in the limit to one-half a printing pitch, thereby permitting a considerable compression of the characters on the type-carrying member without causing the problems of double printing and interference.

The invention description will be completed by a brief reference to the logic and electronic circuits which may be used in a printer for controlling the selective operation of the two printing hammers. FIG. 7 illustrates a circuit for controlling the printing hammers, which is particularly suitable for a serial synchronous printer. A timing disc 61 rotates in synchronism with the character member and in fixed relationship with the movement of the printing carriage. Disc 61 presents a sequence of notches on its periphery, each notch corresponding to a character position on the character member. A sensor 62 generates, in correspondence with the passage of each notch in front of a detecting head 63, an electric pulse, which is applied to the input terminal 64 of an electronic binary counter 65. Counter 65 comprises, for example, six bistable elements and can count from 0 to 63. The disc 61 and the detecting head 63 constitute, in a more general sense, a detecting means for detecting the position of rotation of the type carrying member with respect to a reference point, that is the point at which the sensor 62 is located, or any other point fixedly related to this point.

The six output leads 66 of counter supply a binary code representing the different characters which reach a printing position in successive intervals. The output signals on lead 66 are applied to input terminals of a comparison circuit 69, which receives on other input leads 70 thereof, a binary code representing the character to be printed. When the code of the character in the printing position matches the code of the character to be printed, comparison circuit 69 issues a print command on an output lead 71. In accordance with the instant invention, such print command is applied selectively to one of the two hammers provided on the printer.

The selection of a hammer is accomplished in the following manner: The most significant output signal of counter 65 is coupled on a lead 67 directly to an input lead of a logic AND-gate 72 and through a NOT-circuit 74 to an input lead of an AND-gate 73. The output lead 71 is connected to a second input lead of AND-gates 72 and 73.

The output signals of AND-gates 72 and 73 control respective actuating circuits 75 and 76 of the two hammers.

When the counter 65 supplies a binary code representing the decimal 0 to 31, lead 67 is at the binary level 0, whereupon AND-gate 72 is disabled. Conversely, AND-gate 73 is enabled. If, at this time, the character to be printed has a decimal code between 0 and 31, the print command on lead 71 is transferred through the AND-gate 73 to actuating circuit 76.

When the counter 65 supplies a binary code representing the decimal numbers from 32 to 63, lead 67 is at the binary level 1, whereupon AND-gate 72 is enabled and AND-gate 73 is disabled. If, at this time, the character to be printed has a decimal code between 32 and 63, the print command is transferred through AND-gate 72 to actuating circuit 75.

This selective control of the two printing hammers as a function of the character code provides, as a consequence of the fixed relationship between the movement of the printing carriage and the relation of the typecarrying member, that during a first half-phase of the printing carriage movement from one printing position to the next the first hammer is enabled to print, while during a second half-phase the second hammer is enable to print. In other words, sensor 63, counter 65, inverter 74 and gates 72 and 73 provide control means to selectively actuate the hammers according to the position of the printing carriage relative to a printing position.

It is important to observe that the invention is also applicable to asynchronous printers wherein there is not a fixed relationship between the rotation of the type-carrying member and the movement of the printing carriage. One of such printers is, described for example, in the above-mentioned US. Pat. application Ser. No. 108,787. In this instance, the selective control of the two printing hammers is preferably accomplished by a direct measurement of the printing carriage position. This is illustrated schematically in FIG. 8.

In the circuit of FIG. 8, a timing device 61, together with a detecting head 63, a sensor 62, a counter 65 and a comparison circuit 6? provide for the generation of a printing command on lead 71, as in the circuit of FIG. 7. However, the selection of the printing hammer is accomplished in the following manner:

A second timing device 81, associated with the movement mechanism of the printing carriage, together with a sensor 82 provides an output lead 83, a pulse each time the printing carriage reaches (or overshoots) both a printing position and an intermediate position (for example a position midway between two adjacent printing positions). These pulses are applied on lead 83 to the input terminals of a bistable circuit, or flip-flop, 84, which changes its state upon the reception of each pulse. In other words timing device 8], sensor 82 and flip-flop 84 provide detecting means to detect the position of the printing carriage relative to a printing position. Therefore, on output leads 85 and 86 there occur alternately for a duration of one-half pitch two distinct binary levels 1 and O, which enable alternately two AND-gates 87 and 88. Therefore, the command signals arriving on lead 71 are transferred selectively through AND-gates 87 and 88 to one of the two actuating circuits 89 and 90 of the printing hammers.

In the previous description, reference has been made to a preferred embodiment, and to use of the invention in serial printers using a star-shaped character member. However, it is apparent that changes may be made to the disposition of the hammers, to the control circuits and to the printing devices without departing from the spirit of the invention. For example, the character member may comprise a flexible belt, a cup-shaped element, or an equivalent apparatus. Moreover, the disclosed arrangements of two hammers may be changed; thus, instead of two hammers it is possible to use three or more hammers, suitably staggered and of reduced width, and selectively actuated as described. The disposition of the two hammers on two different levels has been provided by way of example; thus, the hammer heads may designed with a portion cut sideways or with grooves suitably staggered so to permit the relative interposition of the two hammers, which may therefore be assembled on the same plane.

I claim:

1. in a high speed on-the-fly serial printer, wherein character printing is accomplished one character at a time along a succession of printing positions and having a printing carriage movable from one printing position to the next, the improvement comprising:

a plurality of printing hammers mounted on said printing carriage each having a width greater than half the pitch between adjacent printing positions, and being overlapped in part so as to be opposite two adjacent printing position spacings, and

control means for selectively actuating either one or another of said hammers in correspondence with the relative position of said carriage with respect to a printing position, for accomplishing printing in said print position.

2. In a high-speed on-the-fly serial printer, wherein character printing is accomplished one character at a time along a succession of printing positions defining a print line and having a printing carriage movable from one printing position to the next, the improvement comprising:

a pair of printing hammers, each having a width greater than the pitch between adjacent printing positions and being overlapped in part in the direction of the print line, said hammers being mounted on said printing carriage; detecting means for detecting the position of said printing carriage with respect to one of said printing positions and to deliver corresponding signals representing said printing positions and control means responsive to said signals for selectively actuating one or the other of said printing hammers for accomplishing printing in said one printing position.

3. In a high-speed on-the-fly synchronous serial printer wherein the character printing is accomplished one character at a time along a succession of printing positions defining a print line and having a printing carriage movable from one printing position to the next with a movement in fixed relationship with the rotation of a type-carrying member, the improvement comprising:

a pair of printing hammers, each having a width greater than one-half the pitch between adjacent printing positions and being overlapped in part in the direction of the print line, said hammers being on said printing carriage; detecting means to detect the position of rotation of said type-carrying member with respect to a reference point and to deliver corresponding signals; and control means responsive to said signals to selectively actuate one or the other of said printing hammers.

4. in a printer having a carriage movable parallel to a print line comprising spaced apart image receiving locations, and a character member mounted on said carriage comprising a rotatable type-carrying member which presents characters sequentially and cyclically proximate to said print line, the combination comprising;

a plurality of printing hammers mounted on said carriage, each having a width greater than half the pitch between adjacent image receiving locations and being overlapped in part so as to be opposite two adjacent image receiving location spacings, each of said printing hammers being responsive to a respective control signal received thereby to cooperate with the one of said characters proximate to one of said character image receiving locations to form an image of said one character on said print line, detecting means for detecting the position of said carriage relative to said one location and gen erating a corresponding signal and controllable print command control means for receiving said generated signal and delivering a selected one of said control signals in correspondence with the relative position of said carriage with respect to said one character image receiving location. 

1. In a high speed on-the-fly serial printer, wherein character printing is accomplished one character at a time along a succession of printing positions and having a printing carriage movable from one printing position to the next, the improvement comprising: a plurality of printing hammers mounteD on said printing carriage each having a width greater than half the pitch between adjacent printing positions, and being overlapped in part so as to be opposite two adjacent printing position spacings, and control means for selectively actuating either one or another of said hammers in correspondence with the relative position of said carriage with respect to a printing position, for accomplishing printing in said print position.
 2. In a high-speed on-the-fly serial printer, wherein character printing is accomplished one character at a time along a succession of printing positions defining a print line and having a printing carriage movable from one printing position to the next, the improvement comprising: a pair of printing hammers, each having a width greater than the pitch between adjacent printing positions and being overlapped in part in the direction of the print line, said hammers being mounted on said printing carriage; detecting means for detecting the position of said printing carriage with respect to one of said printing positions and to deliver corresponding signals representing said printing positions and control means responsive to said signals for selectively actuating one or the other of said printing hammers for accomplishing printing in said one printing position.
 3. In a high-speed on-the-fly synchronous serial printer wherein the character printing is accomplished one character at a time along a succession of printing positions defining a print line and having a printing carriage movable from one printing position to the next with a movement in fixed relationship with the rotation of a type-carrying member, the improvement comprising: a pair of printing hammers, each having a width greater than one-half the pitch between adjacent printing positions and being overlapped in part in the direction of the print line, said hammers being on said printing carriage; detecting means to detect the position of rotation of said type-carrying member with respect to a reference point and to deliver corresponding signals; and control means responsive to said signals to selectively actuate one or the other of said printing hammers.
 4. In a printer having a carriage movable parallel to a print line comprising spaced apart image receiving locations, and a character member mounted on said carriage comprising a rotatable type-carrying member which presents characters sequentially and cyclically proximate to said print line, the combination comprising: a plurality of printing hammers mounted on said carriage, each having a width greater than half the pitch between adjacent image receiving locations and being overlapped in part so as to be opposite two adjacent image receiving location spacings, each of said printing hammers being responsive to a respective control signal received thereby to cooperate with the one of said characters proximate to one of said character image receiving locations to form an image of said one character on said print line, detecting means for detecting the position of said carriage relative to said one location and generating a corresponding signal and controllable print command control means for receiving said generated signal and delivering a selected one of said control signals in correspondence with the relative position of said carriage with respect to said one character image receiving location. 